This invention relates generally to a new and improved tool or jig designed to lay out the location of treads and risers on the stringers to be used in constructing a stairway. More particularly, the invention relates to an improved stair stringer layout jig in which the tread and riser dimensions may be simultaneously adjusted on both stringers so as to enable uniform tread and riser dimensions over the entire stairway.
The technique of laying out treads and risers on a stair stringer is well known to those skilled in the art. Jigs or tools have been designed to assist in this procedure from the earliest days, as illustrated by exemplary U.S. Pat. No. 796,030 issued to Baumgartner on Aug. 1, 1905, wherein a straight edge is positioned along a stringer, and a carpenter's square is pivoted about a point located within the intersection of its two legs to change the pitch of the stairs, i.e., to change the relative proportions of the length of tread and riser. The jig is moved longitudinally along the stringer to each new tread and riser location and lines scribed on the stringer, which are then either used to cut the stringer or to attach supports for the treads and risers.
A stair layout tool suitable for a metal channel-shaped stringer is shown in U.S. Pat. No. 3,478,434 issued to Catalano on Nov. 18, 1969. In either of the aforesaid tools, the carpenter's square may be pivoted in order to change the pitch (relative lengths of treads and risers) so as to provide an integral number of equally dimensioned steps within the available space. However, when scribing one tread and riser at a time on one stringer, there are minute accumulated errors. In attempting to duplicate the layout on the opposite stringer, variations can occur between the two stringers which are undesirable.
U.S. Pat. No. 3,250,014 issued May 10, 1966 to Watson describes a layout jig for the full length of a stair stringer, enabling all tread and riser dimensions to be simultaneously adjusted for one stringer. However the apparatus is very complicated, has a large number of parts and is able to do only one stringer at a time.
It would be desirable to provide a simplified stringer layout jig, which would insure duplication of results on the two stairway stringers. It would also be desirable to provide an improved stringer layout jig in which the tread and riser dimensions could be adjusted simultaneously and identically on two mating stringers at once.
Accordingly, one object of the present invention is to provide an improved jig for laying out tread and riser locations on a stair stringer.
Another object of the invention is to provide an improved jig for laying out two mating stair stringers simultaneously.
Still another object of the invention is to provide an improved stair stringer layout jig in which tread and riser dimensions may be adjusted on two stringers simultaneously and identically.